(stem sawflies), a family of hymenopterous insects that are pests of cereal plants. The two most harmful species are the wheat stem sawfly (Cephus pygmaeus) and Trachelus tabidus. The wheat stem sawfly is distributed in North America and Europe. In the USSR it is found mainly in the steppe and forest-steppe zones, but it has reached as far as Leningrad Oblast. Trachelus tabidus is found in the south, in the steppe zone of the European part of the USSR. The larvae of the Cephidae damage the stems of many cereal grains, as well as awnless bromegrass, orchard grass, timothy, and wild oats.
Adult larvae winter in the lower part of the stem. In the steppe zone the wheat stem sawfly hatches at the beginning of the heading stage of winter wheat, and Trachelus tabidus 12 to 20 days later. The insects feed for some time on the nectar of the flowers; then the females, after boring through the stem with their ovipositors, lay their eggs in the cavity of the upper parts of the stems. As the larvae feed inside the stems, they destroy part of the vessels that conduct water, and the grain diminishes in weight, as well as in quality. More of the plants with bored-through stems fall, and the fodder quality of the straw deteriorates.
Control measures consist in the careful disking of the stubble and deep autumn moldboard plowing. In all, plowing will kill up to 60 percent of the larvae. Other control measures include the early sowing of spring cereal crops, windrow harvesting of wheat, planting of wheat varieties with developed stems, and early harvesting of cereals.
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V. N. SHCHEGOLEV